This invention relates to a fuel delivery rail assembly for an internal combustion engine, especially for an automotive engine, equipped with a fuel injection system. The fuel delivery rail assembly delivers pressurized fuel supplied from a fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and the fuel supply passages on the engine.
An example of the fuel delivery rail assembly utilized for a straight-type 4 cylinder engine is shown in FIG. 8 of the attached drawings. In this assembly, an elongated conduit 1 having a rectangular or square hollow section with a fuel passage therein extends along the direction of a crank shaft. On the fuel supply side of the conduit 1, fuel is supplied through a fuel inlet pipe 2 connected to the front end of the conduit 1, and on the fuel return side of the conduit 1, remaining fuel is ejected through a fuel return pipe 3. To the bottom side of the conduit 1, four sockets 4 are fixed complying with the predetermined mounting orientations so as to receive associated tips of fuel injectors. The axial directions of the sockets should precisely align with the respective axial direction of the injectors. Furthermore, pitch lengths between adjacent sockets should precisely coincide with the corresponding pitch lengths between associated injectors.
To the conduit 1, two thick brackets 5 are also fixed and project perpendicularly from the conduit 1 for the purpose of connection to the engine.
As shown in FIG. 8, the fuel return pipe 3 is usually perpendicularly attached to the conduit 1. On the other hand, the fuel inlet pipe 2 is attached to the conduit 1 in various fashions, generally via connecting means such as a straight tubular adaptor 6, due to the fact that it is difficult to connect the inlet pipe 2 having a circular hollow section to the conduit 1 having a rectangular or square section.
Another prior art device is shown in FIG. 9, in which connecting adaptors 12 and 13 are welded to the ends of the elongated conduit 1 having a fuel passage 1A therein. The fuel inlet adaptor 12 receives fuel from an associated adaptor 17 through a fuel inlet pipe 18 fixed to a pressure regulator for the engine. The remaining fuel is ejected through a fuel return adaptor 13 fixed adjacent to the distal end of the conduit 1.
The configuration of the fuel inlet adaptor 12 is formed as shown in FIG. 10. To the flat circular rear surface 14 of the adaptor 12, a front edge of the rectangular conduit 1 is attached and welded by brazing work while kept in abutment with the surface 14 to establish a perfect connection.
However, in such conventional assemblies, the inside area of the fuel passage is abruptly restricted within the transition from a fuel inlet opening 15 having an interior diameter D to a smaller hole 16 having an interior diameter d. For example, when the height H of the conduit 1 is 12 mm, the width L is 25 mm, the thickness of the wall of the conduit 1 is 1.6 mm, and the interior diameter D of the opening 15 is 15 mm, the interior diameter d of the hole 16 becomes about 8 mm, resulting in an abrupt decrease of area with a great loss of fuel pressure.
In FIGS. 11A and 11B, undesirable welding patterns of the prior art are shown. When the adaptor 12 is welded to the conduit 1, if the edge surface 19A of the conduit 1 is cut in oblique section FIG. 11A, or the edge surface 19A is contoured in waved fom FIG. 11B, welding defects causing a fuel leakage are liable to occur. Furthermore, such welding patterns are apt to generate misalignment of the axial lines between the adaptor 12 and the conduit 1. Such misalignment causes a defective installation of the fuel delivery rail assembly to the engine. Due to the fact that the adaptor 12 is provided with a stepped interior surface which should be machined smoothly, it becomes costly to manufacture.
In the U.S. Pat. No. 4,457,280 to Hudson, issued July 3, 1984, there is disclosed a fuel rail assembly for holding a plurality of electromechanical fuel injector elements in aligned positions on an internal combustion engine. The beam portion of the fuel rail is comprised of two elongated manifold members with overlapping sides brazed together. Although a fuel inlet nipple is directly inserted into the front end of the beam portion, this assembly is apparently costly to manufacture.
Japanese utility model public disclosure No. 40577/1984 discloses a fuel delivery rail assembly in which both fuel inlet and return pipes are fixed perpendicularly to the conduit. However, in such a design, there is a disadvantage that fuel supply performance is obstructed by back pressure due to a piping resistance.